Improved standards of living and better dental education over the past thirty years have given rise to higher expectations for dental treatment, for example, for safety, durability, and aesthetics. The higher standards demanded by adults are also being applied to their children. The demand for aesthetics and the requirement of durable and proven restorative care present a challenging balance that must be managed.
For over fifty years, stainless steel crowns (SSC) have proven to be some of the most durable and successful posterior restorations for primary teeth. They have been considered to be the best choice of treatment for teeth with multi-surface caries, developmental defects, fractured teeth, abutments for space maintainers and for the best conservation after root canal treatment in primary dentition.
Despite their durable clinical advantages, these types of restorations suffer from two major drawbacks: low aesthetic perception, and Ni-ion release.
Parents often express that they do not like the way that stainless steel crowns look, with the crowns on the lower first primary molars being commented on the most.
There have been several attempts at improving the aesthetics of stainless steel crowns. Open-faced SSCs were an attempt to use composite dental restorative material inserted into a cut window in the crown. The disadvantage of this method is that they are time consuming and the metal window and/or blood may cause discoloration of the composite, which ultimately reduces the aesthetic value.
Stainless steel crowns with bonded composite veneers have been developed as an alternative to open faced crowns. Composite may be bonded effectively to the metal of stainless steel crowns using a bonding agent. Fuks et al. (1999) reported that although aesthetics are improved, occlusal reduction has to be more aggressive, crimping is more difficult, the crowns have to fit passively to avoid facing fracture, the final aesthetic result is not always pleasing, and they are expensive.
If the crowns are being chosen for aesthetic value, the durability of the composite veneer is of clinical importance. Ram et al. (2003) reported that after 4 years, all aesthetic crowns presented chipping of the facing and, consequently, a very poor aesthetic appearance.
As a component of the stainless steel alloy from which they are fabricated, stainless steel crowns contain 9-12% Ni. Despite all the good properties resulting from the presence of nickel, it has a few contraindications for its use. Nickel allergic contact dermatitis is the most prevalent allergy in North America with an incidence of 14.3%. It is known to cause CFS like symptoms, chronic fatigue, fibromyalgia and other diseases of unknown etiology. Children between 8-12 years of age have been documented to have reported a positive patch test for nickel sensitivity (8.1%). 22.97% nickel in intraoral alloys seems to raise circulating eiosinophil, neutrophil and basophil numbers. Even though these crowns provide the best available conservation of the tooth, the Ni ion release from these alloys over time may cause lymphocytic reactivity leading to various major health issues in children.
Other dental and orthopedic devices and materials suffer from some of the same problems identified above with respect to stainless steel crowns.